much anticipated Half-Life mod Black Mesa: Source appears in video form after a long waiting period.

Gameplay footage of the much anticipated Half-Life mod Black Mesa: Source has finally reared its head online, after being posted today on ValveTime.

The short video showing the On a Rail chapter, which is captured from a "fairly old build" of the user mod, was designed using the latest version of Valve's Source engine. However Half-Life fans are already criticising the use of iron sights for the .357 Magnum, a zoom feature made available in the single-player campaign.

A second video posted on LambdaGeneration.com shows poor-quality footage of the Surface Tension chapter, taken from an old and outdated build.

Black Mesa: Source began development eight years ago and currently has no official release date.